Re: [PATCH v2 1/6] powerpc/pseries/iommu: Create defines for operations in ibm,ddw-applicable

From: Alexey Kardashevskiy <aik@ozlabs.ru>
To: Leonardo Bras <leobras.c@gmail.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Thiago Jung Bauermann <bauerman@linux.ibm.com>,
	Ram Pai <linuxram@us.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/6] powerpc/pseries/iommu: Create defines for operations in ibm,ddw-applicable
Date: Thu, 2 Jul 2020 10:43:49 +1000	[thread overview]
Message-ID: <0d3ee444-f528-673e-48f9-633138398543@ozlabs.ru> (raw)
In-Reply-To: <f1f0563dae4c81620b53bcc258f2960a7948a583.camel@gmail.com>

On 02/07/2020 10:36, Leonardo Bras wrote:
> On Thu, 2020-07-02 at 10:21 +1000, Alexey Kardashevskiy wrote:
>>> enum {
>>>        DDW_QUERY_PE_DMA_WIN,
>>>        DDW_CREATE_PE_DMA_WIN,
>>>        DDW_REMOVE_PE_DMA_WIN,
>>>
>>>        DDW_APPLICABLE_SIZE
>>> }
>>> IMO, it looks better than all the defines before.
>>>
>>> What do you think?
>>
>> No, not really, these come from a binary interface so the reader of this
>> cares about absolute numbers and rather wants to see them explicitly.
> 
> Makes sense to me.
> I am still getting experience on where to use enum vs define. Thanks
> for the tip!
> 
> Using something like 
> enum {
> 	DDW_QUERY_PE_DMA_WIN = 0,
> 	DDW_CREATE_PE_DMA_WIN = 1,
> 	DDW_REMOVE_PE_DMA_WIN = 2,
> 
> 	DDW_APPLICABLE_SIZE
> };
> 
> would be fine too?

This is fine too.

> Or should one stick to #define in this case?

imho a matter of taste but after some grepping it feels like #define is
mostly used which does not mean it is a good idea. Keep it enum and see
if it passed mpe's filter :)

-- 
Alexey